Foliar nutrient dynamics and nutrient use efficiency of four deciduous tree species in relation to site fertility.
Seasonal foliar nutrient dynamics of four deciduous forest tree species, Quercus prinus, Q. alba, Acer rubrum and Fagus grandifolia, were examined in neighbouring sites of different soil nutrient availability and pH within Neotoma Valley, southern Ohio, USA. On the less fertile soil, foliar nitrogen and phosphorus concentrations were consistently lower, and leaf mass produced per unit N or P invested greater, in Q. prinus, Q. alba and A. rubrum. Proportional resorption of N and P was greater on the less fertile soil in Q. alba, A. rubrum, and E. grandifolia. Simulated throughfall losses at mid- and late-growing season, as estimated by laboratory leaching of leaves in synthetic rainfall, resulted in lower leaching losses from leaves taken from infertile site trees in ten of sixteen cases. These patterns of nutrient conservation resulted in higher nitrogen growth efficiency (kg wood + leaf produced/g nitrogen lost in litterfall) in all species, and higher phosphorus growth efficiency in all but F. grandifolia, on infertile than fertile sites. Thus these four deciduous tree species exhibited physiological plasticity which allowed maintenance of relative growth rates, despite low soil nutrient availability, by increasing the efficiency of nutrient use. If, as currently projected, long-term acid deposition results in decreasing soil pH and nutrient availability, within some limits, these deciduous tree species may maintain productivity by increasing nutrient use efficiency.